Stabilized lubricating composition



Patented Sept. 26, 1939 uuiraa STATES PATENT OFFICE STABILIZEDLUBRICATING COMPOSITION Louis A. Mikeska, Westfield, and Eugene Lieber,

Linden, N. 3., assignors to Standard Oil Development Company, acorporation of Delaware No Drawing. Application August 1, 1936, SerialNo. 93,764

14 Claims.

the substituent radicals, such as hydroxyl and alkyl, are not limited tothe positions shown 2 therein. These radicals may be connected to anyposition in the benzene ring, but those compounds in which the alkylradicals are in ortho or para position to the hydroxyl group arepreferred. Derivatives of these compounds containing other groupsconnected to either the alkyl groups, the aromatic nucleus, and/or thesulfur group, are also included. For example, the alkyl groups may bearyl-alkyl groups, such as benzyl. Likewise, the sulfur may be wholly orpartially replaced by selenium or tellurium.

It has now been found that the addition of these compounds to minerallubricating oils results in blends which are highly resistant tooxidation and which show a decreased tendency to corrode bearings and toform sludge, particularly in service in lubricating internal combustionengines. Other and further objects of this invention will be apparentfrom the following description and the claims.

The following examples illustrate the use of the compounds describedherein as stabilizing agents in lubricating oils:

EXAMPLE 1 Di-tertiary amyl di-phenol disulfide was dissolved, in 0.2%concentration, in a highly refined S. A. E. 20 petroleum lubricating oilhaving a Viscosity Index of 90. A similar solution was prepared with thesame oil and di-tertiary butyl di-phenol disulfide. These solutions areindi cated by the Blends A and B, respectively, in the following table.The improvement in the stability of the blend is indicated by thefollowing results of tests on the original oil and the blend.

a Blends Original 011 Corrosion Passes Passes Passes Sligh number.. 24.11 18. 3 Cone number. 0. 45 0. 0. 17 Lead tolerance. 0.005 0.025 0. 030Oxidation rate 235 4-7-1348 18-18-1648 The methods of testing used inthe above example are as follows:

Cone test This methodis a means for determining the tendency of an oilto deposit solid matter upon heated metallic surfaces. dropping the oilto be tested over a heated metal (generally steel) cone, having acircumferential groove milled out in a screw fashion on the periphery soas to allow a time of contact of about one minute between the heatedsteel surface and the oil. A total volume of 60 cc. of oil is droppedfrom a dropping funnel during a period of 2 hours to obtain this time ofcontact. The temperature of the cone may be any desired value, but forlubricating oils 250 C. is preferable since it represents approximatelythe extreme temperature to which oils are exposed in ordinary engineuse. The cone is weighed before the test. After all the oil is run overthe metal surface, the cone is washed with naphtha to remove adheringoil and the total deposit left is obtained by dif This value isgenerally reference in weight. ported in grams.

It consists in slowly The test does not appear to have any relation tothe oxygen absorption test, since it is possible to have two compoundsgiving the same cone deposit in lubricating oils, but having widelyvarying oxygen absorption rates,

and vice versa.

Sligh test This test of the tendency of an oil to sludge under oxidizingconditions is described in Proc. A. S. T. M. 24, 964, II (1924), exceptthat the oxidation is conducted for 24 hours.

Oxygen absorption test This test is used for the most part in judgingthe susceptibility to oxidation and acid formation of a lubricating oilat elevated temperatures.

The resuls are generally given as the number of cc.s of oxygen absorbedby 10 cc. of an oil per 15 minute. interval at 200 C.

Corrosion Test This consists in immersing a bright copper strip forthree hours in the oil maintained at 212 F. It is used to determine thepresence of corrosive sulfur in oil, which is indicated by discolorationor pitting of the copper strip.

Lead Tolerance Test This test is used to determine the tendency of anoil to corrode bearings. It is also known as the Underwood Test. 1500cc. of the oil is maintained at 325 F. and is sprayed for 5 hoursagainst two each of copper-lead and cadmiumsilver alloy bearings. Theoil dripping from the bearing is recirculated. The bearings are weightedbefore and after the test to determine any loss in weight. The test isthen repeated with addition of a soluble lead compound, pref erably leadoleate, in increments of 0.005% by weight of lead. A loss in weight of50 mg. indicates the lead tolerance of the oil has been exceeded, andthe amount of lead added in the previous test is recorded as the leadtoleranceif A lead tolerance below 0.020 is considered unsatisfactory.

EXAMPLE 2 Runs under closely comparable conditions were made in a C. F.R. (Cooperative Fuel Research) engine with a highly refinedMid-Continent lubricating oil of 72 seconds Saybolt viscosity at 210 F.,and with blends of the same oil and di-tertiary amyl di-phenoldisulfide. After each run the engine was taken down, inspected and ratedby demerits according to the condition of the piston parts, valves andcylinder. On this scale the demerit rating is higher as the enginecondition is worse. The runs were each made for 14 hours at a jackettemperature of 375 F. The results are given below:'

C. F. R. engine tests Blends with amyl phenol Blank disulfide Demeritrating 5.54 3.93 2.70

Other alkyl phenol polysulfides may also be used for preparing improvedlubricating oil compositions of high stability in the manner describedin the above examples. Such compounds preferably have at least one alkylgroups of about 2 to 8 carbon atoms. Compounds containing two alkylphenol groups in which the alkyl radicals contain about 4 to 6 carbonatoms are preferred. The alkyl groups may be normal, 150, secondary ortertiary. They may also be cyclo but the open chain alkyl groups arepreferred. The polysulfide compounds may be either symmetrical orunsymmetrical, i. e., containing different alkyl and/or aryl radicals.The aryl radicals may be polyhydroxy including such groups as thosederived from resorcinol, hydroquinone and their alkylated and arylatedderivatives. They may also contain condensed aromatic nuclei such asthose derived from naphthol and its corresponding derivatives.

One suitable method for preparing the alkyl phenol polysulfides whichare used in this invention is to react alkyl phenols with sulfurmonochloride. This reaction is preferably conducted in the presence ofan inert'diluent, preferably in alkyl halide such as ethylene chloride,which boils at the reaction temperature and is con densed under refluxwhile withdrawing the evolved hydrogen halide from the reaction zone.When the reaction is completed, as evidenced by the failure to liberatefurther hydrogen halide, the solvent and any unreacted phenol areremoved by distillation and the polysul'fide is obtained as adistillation residue.

Suitable alkyl phenols for use in this reaction may be prepared bycondensing phenols with olefines of preferably 2 to 8 carbon atoms orwith mixtures thereof. Such olefines are readily obtained in thecracking of petroleum oils and waxes.

The reaction of the alkyl phenol and sulfur monochloride is preferablyconducted with a ratio of between about 0.4 and 0.6 mol of sulfurmonochloride per mol of alkyl phenol. The use of higher ratios leads tothe formation of resins which are insoluble in petroleum lubricatingoils. G

Even with the preferred ratios a small proportion of polymers such asdimers and trimers are obtained along with the desired product. Suchrelatively low molecular weight polymers are soluble in petroleumlubricating oils and are not objectionable in the product. In fact, ithas been found that in some instances their presence is advantageous.

The reaction may also be conducted with a mixture of sulfur monochlorideand sulfur dichloride, in which mixture the proportion of the latter isusually less than 0.75 and is preferably about 0.10 to 0.35, based onthe total sulfur halide used. In using this mixed reagent their isobtained as a reaction product a mixture of alkyl phenol disulflde withan amount of alkyl phenol monosulfide corresponding to the proportionsof the respective sulfur halides used. Lubricating oil blends containingthis mixed product exhibit even less corrosion tendencies than thosecontaining only the alkyl phenol disulfide.

The use according to this invention of other derivatives of the alkylphenol polysulfides which contain other substituent groups in additionto the hydroxy and alkyl groups, is also contemplated. Such additionalsubstituent groups should not, however, offset the solubilizing effectof the alkyl groups to an extent suflicient to render the compoundinsoluble in lubricating oil. Examples of suitable groups or radicalswhich may be attached to either the aryl or the alkyl group, areradicals containing oxygen such as ether, aldehyde, ketone, acid andester radicals. those containing nitrogen such as amines and ON andthose containing sulfur, selenium, tellurium and the like.

The sulfur atoms present in the polysulfide linkage of the alkyl phenolpolysulfides may also be wholly or partly replaced by the heaviernonmetallic elements of group 6, such as selenium and tellurium.

While these compounds, or mixtures thereof with other members .of thesame class, with polymers thereof, and with the. alkyl phenolmonosulfides, may be added in any desired concentration within theirsolubility limits to lubricating oils, they are preferably used inconcentrations of about 0.1 to 2.0% a concentration of about 0.5% willbe found sufficient to stabilize the majority of petroleum lubricatingoils.

These compounds greatly stabilize mineral lubricating oils at elevatedtemperatures, especially the highly refined oils such as synthetic oils,solvent extracted oils obtained by treatment of mineral lubricating oilswith single solvents such as phenol, dichlorethyl ether, furfural,propane, nitrobenzene, crotonaldehyde, etc., or by double or multiplesolvents such as propaneoresol, etc., clay or acid treated oils, alsoaluminum chloride treated oils, white oils, hydrogenated oils, and thelike. These compounds are especially efiective with such oils havingviscosity indices above 60, 80, 100 or more. Lubricating oils alsostabilized by these compounds are other mineral oils of over orviscosity Saybolt at 210 F., and even those having a viscosity of over100 seconds at 100 R, either in the crude form or partially or highlyrefined by distillation, voltolization, chemical reagents, andadsorptive agents, as well as coal tar or shale distillates, pale oils,neutrals, bright stocks and other residual stocks, cracking coil tarfractions, condensed or polymerized fractions, and the like, eitherwaxy, dewaxed, or non-waxy. The lubricants to which these stabilizingagents are added may also contain dyes, metallic or other soaps, pourinhibitors, sludge dispersers, oxidation inhibitors, thickeners, V. I.improvers such as soluble linear polymers, oiliness agents, resins,rubber, fatty oils, heat thickened fatty oils, sulfurized fatty oils,extreme pressure lubricating agents, organo-metallic compounds, brightstocks (such as refined petroleum lubricating oil residues), voltolizedfats, mineral oils and/or waxes, colloidal solids such as graphite, zincoxide, etc., and the like.

Especially desirable lubricating compositions may be prepared by addingto lubricating oil both an alkyl phenol polysulfide and an oilinessagent, such as a suitable organic ester. Examples of such esters areesters of fatty acids of above about 10 carbon atoms with alcohols.Esters of the acids obtained by limited oxidation of parafiin wax may beused, for example, the isopropyl esters of oxidized wax acids which aresubstantially monobasic. The hydroxyl groups of the alkyl phenolpolysulfides may also be partially or completely esterifled with anorganic acid, preferably a fatty acid. These esterified compounds may bemixed with other non-esterifled alkyl phenol polysulfides. The oilinessagent may be used in any suitable concentration. The amount used isusually between 0.1 and 5.0% of the total composition, and 0.5, 1.0 to2.0% is generally sumcient.

A preferred method for preparing compounds suitable for use in thisinvention is as follows:

EXAMPLE 3 One molal proportion of tertiary amyl phenol is dissolved inethylene chloride and the solution is heated to boiling under reflux. Asolution of molal proportion of sulfur monochloride in ethylenedichloride is then added slowly with stirring to the boiling solution ofamyl phenol. The hydrogen chloride gas evolved during the reaction iswithdrawn from the reaction zone through the reflux condenser. When theaddition of sulfur monochloride solution is completed, the boiling ofthe reaction mixture under reflux is continued for aboutsix hours oruntil no further emission of hydrogen chloride is detectable. By thismeans all the hydrogen chloa product consisting substantially of thedesired amyl phenol disulfide. This product is a dark brown to reddishcolored viscous liquid, which is soluble in most organic solvents,including petroleum and fractions thereof such as gasoline, kerosene,burning and Diesel oils, and lubricating oils. The crude product may beused directly as obtained or after any desired purification, as bytreatment with selective solvents or adsorptive materials such as clay.

Higher polysulfides suitable for use in the present invention may beprepared by condensing alkyl hydroxy thiophenols with sulfurmonochloride or sulfur dichloride. The alkyl hydroxy thiophenols may beobtained by reduction either of the alkyl phenol disulfides describedabove or of alkyl phenol chlor sulfonic acids. These reactions may beillustrated as follows:

R and R in the above formulae have the same significance as in the firstformula presented herein. Reactions 2 and 3 may be conducted under thesame conditions described in Example 3, using half the molal proportionof the sulfur halide.

These tri and tetra sulfides may be used as blending agents withlubricating oils in the same manner already described for thedisulfides.

This invention is not to be limited to any specific examples orexplanation, all of' which are presented herein solely for purpose ofillustration, but is limited only by the following claims, in which itis desired to claim all novelty in so far as the prior art permits.

We claim:

1. An improved lubricating composition comprising a mineral lubricatingoil having dissolved therein a small amount sufficient to increase thestability of said oil of an alkyl phenol polysulfide of the formula inwhich R and R are alkyl groups having at least 2 carbon atoms each and nis an integer, from 2 to 4.

2.2 Composition according to claim 1 in which n:

3. Composition according to claim 1 in which n=2, and R and R are alkylgroups of 2 to 8 carbon atoms each.

4. Composition according to claim 1 in which n=2 and R and R arebranched alkyl groups.

5. Composition according to claim 1 in which said mineral lubricatingoil is a highly refined petroleum lubricating oil having a ViscosityIndex above 80.

6. A mineral lubricating oil containing about 0.01 to 1%.01 a dialkyldiphenol disulfide, in which the alkyl groups contain about 4 to 6carbon atoms each.

7. An improved lubricating composition comprising a mineral lubricatingoil having dissolved therein a small amount of diamyl diphenoldisulflde.

8. An improved lubricating composition comprising a highly refinedpetroleum lubricating oil having dissolved therein a small amount ofditertiary amyl diphenol disulflde.

9. An improved lubricating composition comprising a mineral lubricatingoil having dissolved therein a small amount of dibutyl diphenoldisulfide.

10. An alkyl polysulfide having the formula l in'which R and R are alkylradicals of about 2 to 8 carbon atoms each and n is 2 to 4.

11. A composition of matter comprising a mineral lubricating oilcontaining dissolved therein, in an amount sufficient to increase thestability of said oil, an alkyl phenol polysulfide in which pairs ofalkyl phenol groups are interlinked by a plurality of sulfur atoms, saidalkyl phenol groups being composed of an aromatic nucleus containing ahydroxyl substituent group and an alkyl substituent group having atleast 2 carbon atoms.

12. A composition of matter as described inclaim 11 in which about 0.01to 1% of the alkyl phenol polysulilde is contained in the lubricatingoil.

13. A composition of matter comprising a mineral lubricating oilcontaining dissolved therein about 0.01 to 1% of an alkyl phenoldisulflde in which pairs 01' alkyl phenol groups are interlinked by twosulfur atoms, each alkyl phenol group being composed of an aromaticnucleus containing a hydroxyl substituent group and an alkyl substituentgroup having at least two carbon atoms.

14. An alkyl phenol disulflde which is composed of a pair oi! aromaticnuclei interlinked through 2 sulfur atoms, each aromatic nucleuscontaining a hydroxyl substituent group and an alkyl substituent groupcontaining 2 to 8 carbon atoms.

LOUIS A. IVIIKESKA. EUGENE LIEBER.

